[Severe form of juvenile type II glycogenosis in a compound-heterozygous boy (Tyr-292--> Cys/Arg-854-->Stop)].

INTRODUCTION: Type II glycogenosis is a glycogen storage disease inherited as an autosomal recessive trait. This molecular and clinically heterogeneous condition is due to a deficiency in a lysosomal acid 1,4-alpha-glucosidase. OBJECTIVE: To report the clinical, enzymatic and molecular characterization of a mulatto child, born to healthy Dominican mother and Caucasian father, affected by the juvenile phenotype form of type II glycogenosis. CLINICAL CASE: This 16-month-old male presented from 10 months with motor delay, limb-girdle hypotonia, prominence of calves, increased CPK value, mixed myotonic/myopathic pattern on EMG, intense glycogen muscle storage (775 micrograms/mg of protein) and severe deficiency of 1,4-alpha-glucosidase activity ( Cys, coming from the father, and Arg-854-->Stop, coming from the mother and previously reported in two Afroamerican patients, one with the adult phenotype and the other with the juvenile one. CONCLUSIONS: The present case corresponds to a severe form of type II juvenile glycogenosis. The severity of this condition may be related to the observed mutations and the associated extremely low muscle enzymatic activity.